The present invention relates to a data compressing system and more particularly a data compressing system for compressing data with a high correlation between adjacent sampling points, such as audio signals or video signals.
In recording, reproducing or transmitting an audio signal sampled and digitized, the audio signal is sampled at a sampling period of 8 kHz and the sampled audio data is then quantitized with an accuracy of 8 bits. In order to quantitize the audio signal, a data processor is, therefore, required which is able to process the data of 64K bit per second. The processor for processing a large amount of data is necessarily of the large-sized type. Many data compressions for reducing the data amount per second have been proposed with an intention of saving a capacity of a recording device or narrowing a frequency band-width in a communication line. A PARCOR system, for example, has attracted attention, in which characteristic parameters are extracted from an audio signal through a predetermined information processing scheme and those parameters extracted are composed to produce composed parameter data and the composed parameter data is reproduced to the original information signal. According to the PARCOR system, the data can be remarkably compressed into 2 to 4K bit per second. In the PARCOR system, however, special signal processings are required for the extraction and composition of the characteristic parameters, resulting in a complicated recording and reproducing apparatus. Improvement of the clearness of the reproduced information makes the signal processing considerably complicated and requires a lot of signal processing tasks.
There is another data compressing system proposed, for example, a format composition system. This system, however, involves similar problems of the PARCOR system.